1. feeling dizzy or faint; having a sensation that one might lose consciousness
2. lacking seriousness; frivolous or silly

Examples

• She felt lightheaded after standing up too quickly.
• The medication made him lightheaded and nauseous.
• I get lightheaded when I don’t eat breakfast.
• The heat made everyone feel lightheaded during the parade.
• His lightheaded jokes weren’t appropriate for the serious meeting.
• Don’t be so lightheaded about this important decision.